Technical Field
Embodiments of this disclosure relate to electronic circuits, and more particularly, to transconductance amplifiers and/or to paths between an oscillator and a mixer.
Description of the Related Technology
A front end of a receiver can include a low noise amplifier, mixers to downconvert received signals, a local oscillator, and a signal path from the oscillator (OSC) to the mixer in which the signal path provides a local oscillator (LO) signal to the mixer. The front end of a radio frequency (RF) receiver typically amplifies and mixes RF signals received by way of an antenna. A low noise amplifier can amplify the received signals and provide the amplified signals to mixers. In demodulating RF signals, a mixer can downconvert RF signals to an intermediate frequency (IF), which is lower than the frequency of the received RF signal, by mixing the RF signals with a signal from an LO.
One form of a low noise amplifier is a low noise transconductance amplifier (LNTA). A LNTA amplifies RF signals received from an antenna and then provides an amplified RF current signal, which can be applied to a mixer.
Transconductance amplifiers provide an output current as a function of input voltage, and a common measure of transconductance in an amplifier and in a LNTA is its transconductance (Gm) transfer function. In addition to Gm transfer function, other characteristics of an LNTA also include noise performance and linearity. For quality reception and demodulation, an LNTA with a relatively low noise factor (NF) with low distortion is typically desirable.
In a receiver, the process of demodulation typically involves a mixer. Mixers can downconvert an input signal based on a signal from a LO. In some instances, separate mixers can be used to downconvert RF signals by different amounts so that the mixer outputs are at IF. For instance, one mixer can be used to downconvert RF signals in a high frequency band and another mixer can be used to downconvert RF signals in a low frequency band that is lower than the high frequency band. The LO signals provided to these mixers can have different frequencies and these LO signals can be generated by processing an output signal from a single OSC.